Why cant i see the smoke effect?
If you are talking about the Blender Guru video, this is the top comment from user  r19790606:


  If you can't see smoke and fire you probably use new version of
  blender (2.82). Correct instruction for 2.82:
  
  
  Add monkey
  select monkey in object mode
  F3 -> add Quick Smoke
  (different to video) select monkey 
  choose Physics->Setting->Flow Type : "FIre + Smoke"
  (different to video) select "Smoke Domain" object
  in physics panel click "Bake Data" and wait... (progress in status bar on the bottom)
  after it 's finished click play to start animation.
  
  
  video: https://youtu.be/XN6ClIdL8yw
  
  ps : default only 50 frames are animated. you can change this in phisics->cache-> Frane End (you have to Resume or Free and Bake again ... see point 7)